Bally 742A problems

[mtbeck]

I have a Bally 742A 29C.  When I plug it in it blows the 5amp fuse.  I found out that when I disconnect the ground on the chassis it does not blow the fuse and only the 6v lights come on.  The transformer is 120/50/6 volts 122101.  Could the transformer be bad?  If so, anyone have one to sell?

Thanks,
Darrell

[BigWick]

Does your multimeter show continuity between AC line/Neutral and the transformer core? What happens if you disconnect the AC taps on the transformer and test for a short to ground?

[mtbeck]

Will check tomorrow,
Thanks

[DavidLee]

Before plugging the machine in, install a new fuse if needed.
Pull the reels and hopper out of the machine.

Plug the machine in.
This could eliminate the transformer as being the problem.

If the fuse doesn’t blow.

Inspect the hopper while out of the machine for any burnt wires or coils.
Do the same for the reels.
Inspect the inner side of the door for the same, plus the door plugs for evidence of excessive heat.
Also, look closely at the wires at the left side door hinges and the metal case edge for burn marks.

[wolftalk]

which 5A fuse is blowing?  Both the 120V and the 6V fuses are 5A.

the 120V fuse should have the black wire from your power cord connected to it, and the other side of the 120V fuse is a white/blue wire.

the chassis should not be energized, so if the 6V fuse is the one that is blowing, look for lamp sockets that are touching metal they shouldn't.

I have a 742A-29C schematic, but it'll take a couple days to clean up and post onto https://bingo.cdyn.com/slots/

there is a 742A-29C (T) ... it has a jackpot bell and light tower.  You don't have that one, right?

[mtbeck]

I disconnected the AC taps on the transformer, and there was no short to ground.

I also pulled both the reels and hopper out and it still blows the AC fuse.  I inspected the door, and could not find any indication of any burn marks, and when the fuse blows no indication of smoke or spark.  Will continue to check wiring. 

[wolftalk]

it's the 120V fuse blowing?

with the hopper and reels out, there's not much in the 120V circuit - just the safety timer and the flourescent lamps/starters/ballasts.  Could also be a wiring issue on the back of the hopper plug.

the safety timer is under the transformer, and it looks like either the timer is missing or it's loose behind the metal plate.  Suggest you look at the timer first ... it should look like the below pic.

the timer is not critical to game operation ... if it's missing the white/blue wire from the fuse should connect to the white wire going to the transformer tap (one way or another ... the white wire from the transformer (and flourescents and hopper plug) could just attach to the 120V fuse, and the black wire from the power cord attached to the other end of the 120V fuse).

the 120V stuff is the same in the 742A-1G ... https://bingo.cdyn.com/slots/742A-1G/ - the w-1046-xxx file is the schematic.

[DavidLee]

Possibly the person that removed the timer reattached the wires incorrectly.
Maybe theses photos can be helpful.

[mtbeck]

Thanks for the info and pictures.  I disconnected the two wires from the transformer, one was not to ground, but the other was.  I traced the wire to the fluorescent lamp on the top of the machine, and found a wire shorted to chassis.  I am going to replace the wiring and try again.  Thanks again for the help.
Darrell

[mtbeck]

Found the short, and fixed it.  It seem that it works, except for the handle release reset coil seems weak, and will not armature down to release the latch arm.  I checked the voltage and it is 28 volts, and it should be 50.

[wolftalk]

28V on the coil when it should be powered means a switch or plug connection is cruddy or open.

there's a 2400ohm resistor from the handle release coil to yellow wire 30 (the transformer neutral), so you always see some voltage on the handle release coil.

problem is half the switches in the machine are in the handle release circuit, but if the game pays, then some of them are ok.

the circuit is the same as the 742A-1G referenced in post #6, so if you are comfortable with the schematic you can put a voltmeter probe on orange wire 70 on any handy coil and poke around in the circuit from wire 57-1 on the payout relay down to the handle release coil.

the wire id mappings to wire colors is a chart on the schem.

if you aren't familiar with the schematics but have a voltmeter, check for 50VAC with one probe clipped onto the orange wire (70) on the handle release relay, and the other probe on each wire on the dashpot switch (vertical switch hanging down on right side of reel mech).  That'll divide the remaining switches in half.

if you want to just inspect switches, you care about:
- payout relay (grey to white/orange wires)
- rejector armature switch (white/orange to yellow/brown)
- coin relay (yellow/brown to blue/white)
- dashpot switch (blue/white to white/red)
- reel mech D ( white/red to white/blue)
- handle release coil (white/blue attached to lug)

[DavidLee]

Try cleaning the related contacts.
As they attract more debris being in the horizontal position.

[mtbeck]

Did some more checking and cleaning of contacts.  I did find 50 volts from the Handle Release Reset Coil and Coin Release Switch, so I tried a continuity check of the reset coil and found an open, so the coil must be bad. 

[wolftalk]

make sure ya dig your probe tips thru the oxidation when checking continuity.

if the coil is bad, take a close look at the coil wire itself and where it attaches to the lugs.  If the coil wire broke, you have a 50-50 chance that you can unwrap a turn of wire from the coil, gently scrape off the varnish with a razor (scrape and roll the wire on a flat surface to remove most of the varnish from all around the wire), and solder the wire back onto the lug.  Leave some slack in the wire so the vibrations don't break it again.

the reason you have a 50-50 chance is one end of the coil wire is on the outside and the other end is around the spool under the rest of the wire.  You rarely can pull out a turn if the broken end is the one that's the first windings around the spool.

if you're really desperate, you can unwind the wire onto some kind of rod (like a big drill bit), then rewind it back onto the relay coil spool.  It's easier to buy a new coil :-)

the original coil was E-184-218 or E-184-224A, and the new part number is F-31-2100.  If you can't find an F-31-2100, action pinball suggests a G-31-2100, which is about 1/16" shorter but should be fine.  You could always shim it up with a washer if necessary, but if you do use a plastic washer.

if no luck finding that, the new coil part numbers are spool-wire gauge-number of turns, so you could just pick an F or G spool coil with something close-ish to an F-31-2100.  The coil is only briefly powered, so it's not a big deal if it pulls a bit more current.

if you're back to desperate, you could buy new 31 gauge magnet wire and wrap 2100 turns of it around your existing spool. 

[mtbeck]

Thanks for all your help! 

[mtbeck]

Would the g-31-2000 work for the 184-224?  Having trouble finding F-31-2100, E-184-224 or G-31-2100.

[wolftalk]

yup, close enough.  Less turns of wire will mean a little more current draw and more powerful yank down on the armature plate, but it's not significant.

[DavidLee]

Not clear if you checked the lead wires from the solder lug to the coil.
These thin wires can break loose from the solder joint and not be noticeable.

[mtbeck]

I
 checked the coil solder joints, and also scraped the wires leading to the terminals and tested for continuity, and still no luck.  Did not try to unwind, instead will see about buying another coil.